1. Field of the Invention
The present invention relates to a current-perpendicular-to-the-plane (CPP) structure electromagnetic transducer element comprising an electromagnetic transducer film such as a spin valve magnetoresistive film or a tunnel-junction magnetoresistive film, and upper and lower electrically-conductive lead layers interposing the electromagnetic transducer film in the vertical direction perpendicular to the electromagnetic transducer film.
2. Description of the Prior Art
A single domain property should be established in the free ferromagnetic layer of a magnetoresistive layered stripe such as a spin valve film, a tunnel-junction film, and the like. This single domain property is supposed to greatly contribute to reduction in Barkhausen noise. A pair of biasing hard stripe layers or so-called domain control layers are designed to interpose the spin valve film or the tunnel-junction film so as to realize the single domain property in the free ferromagnetic layer. The magnetoresistive layered stripe or film and the biasing hard stripe layers are usually arranged side by side over a flat surface. For example, the flat surface can be defined on the upper surface of a lower electrically-conductive lead layer in the CPP structure electromagnetic transducer element.
When the magnetoresistive layered stripe or film and the biasing hard stripe layers are formed over the lower electrically-conductive lead layer, the magnetoresistive layered stripe or film is forced to contact the lower electrically-conductive lead layer over the entire bottom surface. Specifically, the extent or size of the magnetoresistive layered stripe or film necessarily determines the size of the path for a sensing electric current. If a further reduction in the path for the sensing electric current is intended, the magnetoresistive layered stripe should further be reduced in size. The reduced path for the sensing electric current leads to a still higher sensitivity of the electromagnetic transducer element in reading the magnetic bit data out of a recording medium.
It is accordingly an object of the present invention to provide a current-perpendicular-to-the-plane structure electromagnetic transducer element greatly contributing to reduction of the path for an electric current supplied to an electromagnetic transducer film without relying on a further reduction in the size of the electromagnetic transducer film.
According to a first aspect of the present invention, there is provided a current-perpendicular-to-the-plane (CPP) structure electromagnetic transducer element comprising: a lower electrically-conductive lead layer; an electrically-conductive terminal piece standing on the surface of the lower electrically-conductive lead layer; an insulation layer spreading over the surface of the lower electrically-conductive lead layer and contacting the side surface of the electrically-conductive terminal piece; an electromagnetic transducer film extending at least across the top surface of the electrically-conductive terminal piece; and an upper electrically-conductive lead layer contacting the upper surface of the electromagnetic transducer film.
The contact established between the electrically-conductive terminal piece and the electromagnetic transducer film is allowed to define the path for the electric current in the CPP electromagnetic transducer element of this type. The electrically-conductive terminal piece is designed to contact the electromagnetic transducer film at the top surface. The contact area of the top surface of the electrically-conductive terminal piece is allowed to determine the size or extent of the path for the electric current through the electromagnetic transducer film. In this manner, the path of the electric current can be reduced in the CPP structure electromagnetic transducer element without relying on reduction in the size of the electromagnetic transducer film.
When the path of the electric current is to be reduced in the CPP structure electromagnetic transducer element, the electromagnetic transducer film may have a second width larger than a first width of the electrically-conductive terminal piece. Reduction in the first width of the electrically-conductive terminal piece serves to reliably establish a reduced path of the electric current between the electromagnetic transducer film and the electrically-conductive terminal piece irrespective of the extent of the second width of the electromagnetic transducer film. The size or extent of the reduced path is allowed to correspond to the extent of the first width.
A flat surface may continuously be defined on the top surface of the electrically-conductive terminal piece and the upper surface of the insulation layer. When the electromagnetic transducer film is formed on the flat surface, it is possible to establish the electromagnetic transducer film at a higher dimensional accuracy. The electromagnetic transducer film may be a magnetoresistive layered stripe or film such as a spin valve film, a tunnel-junction film, and the like.
The lower electrically-conductive lead layer may be made from a magnetic material, for example. Specifically, the lower electrically-conductive lead layer may have not only a property of electric conductors but also a magnetic property. The lower electrically-conductive lead layer of this type is allowed to function as a magnetic shield layer for the electromagnetic transducer film. This greatly contributes to reduction in a so-called read gap in the CPP structure electromagnetic transducer element. The reduction in the read gap leads to a higher linear resolution of the magnetic recordation or data along the recording tracks on a magnetic recording medium.
The upper electrically-conductive lead layer may comprise a terminal bump contacting the electromagnetic transducer film by a third width smaller than the second width. The electrically-conductive terminal bump serves to reduce the contact area between the electromagnetic transducer film and the upper electrically-conductive lead layer. Reduction in the third width of the terminal bump is allowed to establish a reduced path of the electric current between the electromagnetic transducer film and the terminal bump irrespective of the extent of the second width of the electromagnetic transducer film. The size or extent of the reduced path is allowed to correspond to the extent of the third width.
According to a second aspect of the present invention, there is provided a method of making the aforementioned CPP structure electromagnetic transducer element. The method may comprise: forming an electrically-conductive piece on the surface of an electrically-conductive lead layer; forming an insulation layer on the surface of the electrically-conductive lead layer so as to cover the electrically-conductive piece with the insulation layer; subjecting the insulation layer to a flattening treatment so as to expose the top surface of the electrically-conductive piece at a flattened surface defined over the insulation layer; and forming an electromagnetic transducer film on the flattened surface so as to allow extension of the electromagnetic transducer film at least across the top surface of the electrically-conductive piece. In particular, the method allows the formation of the electromagnetic transducer film on the flattened surface, so that the electromagnetic transducer film can be obtained at a higher dimensional accuracy. Here, the electrically-conductive piece turns into the aforementioned electrically-conductive terminal piece.
The method may further comprise: forming the electrically-conductive lead layer according to a predetermined pattern on a surface of a fundamental layer prior to formation of the electrically-conductive piece; forming a basement insulation layer on the surface of the fundamental layer so as to cover the electrically-conductive lead layer with the basement insulation layer; and subjecting the basement insulation layer to a flattening treatment so as to expose the surface of the electrically-conductive lead layer at a flattened surface defined over the basement insulation layer. In particular, the method allows the formation of the electrically-conductive piece on the flattened surface, so that the electrically-conductive piece can be obtained at a higher dimensional accuracy.
Furthermore, the method may further comprise: forming an overlaid insulation layer covering over the electromagnetic transducer film; forming a contact bore penetrating through the overlaid insulation layer so as to expose an upper surface of the electromagnetic transducer film; and filling the contact bore with an electrically-conductive material. The method contributes to a facilitated formation of the aforementioned terminal bump on the upper electrically-conductive lead layer.